Optical waveguide component is a necessary component for optical communication coupler and splitter. A structure of such optical waveguide component comprises a core layer and an outer layer in which a refraction index of the core layer is larger than the outer layer, thereby light can transmit through a full reflection.
Conventionally, the optical waveguide component is prepared from silicon dioxides material by Chemical Vapor Deposition (CVD), Flame Hydrolysis Deposition (FHD), Vacuum Deposition (VD), Sputtering method, or Spin-on Glass (SOG) methods to form an optical communication waveguide material. To adjust a refractive index of the silicon dioxides as a core layer or as an outer layer, the silicon dioxide is usually doped with minor amount of other oxide such as titanium dioxide. However, preparation of the waveguide material by CVD, FHD, VD, and Sputtering method is high cost since the used equipment is complicated. Also, a waveguide material prepared from pure inorganic silicon dioxide by Spin-on Glass (SOG) method encounters with a problem of insufficient thickness. Recently, since optical communication elements have been demanded increasingly, a waveguide component based on polymeric material has been paid attention due to its low cost and easily processing. Some polymeric materials have been proposed in many patents publication, such as acrylates (U.S. Pat. No. 5,062,680), polyimide (U.S. Pat. Nos. 5,108,201; 5,572,619; 5,598,501; and 5,659,648), polysiloxane (U.S. Pat. No. 5,972,516) etc. However, a carbon-hydrogen bond vibration energy of the polymeric material will be lost largely at wavelengths of 1310 nm and 1550 nm which are the wavelengths of light source used in current optical communication, therefore application of the optical waveguide component is greatly limited. An improved proposal has been proposed that use of a fluorinated polymeric material such as fluorinated acrylate and fluorinated polyimide could reduce its light-transmission loss due to a carbon-fluorine bond substituting for the carbon-hydrogen bond present in polymeric material. However, a fluorinated monomer is expensive and its synthesis is difficult, which in turn limits the application of the fluorinated polymeric material in waveguide field. Furthermore, disadvantages of the fluorinated polymeric optical waveguide component are directed to its insufficient heat-resistance and mechanical property. Therefore it is difficult to prepare a channel waveguide from such a fluorinated polymeric material.
Under the above circumstances, the present inventors have conducted an investigation on a composite film to resolve the problems in question, and found that an optical film of acrylate/titanium alkoxide having high light transmittance and flatness can be prepared by combining acid-free catalytic solgel method, polymerization, coating, and multistage baking. Also, due to its low optical transmittance loss, it can further be processed into optical waveguide component.